They are made for a 10+ Mustang, anybody run something similar?

Size:    19x8.5    
Placement:    Front and Rear    
Back Spacing:    5.93" (151mm)    
Offset:    +30mm (1.2")
Bolt Pattern:    5x4.5" (5x114.3mm)   

Offset will push the rim out to the fender real good, bolt pattern is correct..not sure on the backspacing.

2013 SHO PP is 20x8 with offset of 39

I am running 18" X 9"  32 offset rims on my Flex.  They are pretty much flush with the fenders.

Are you lowered with Eibach or H & R springs?  I am, but am running 27" tall tires vs stock at 29".  While it is unlikely, the stock tires might rub while turning, especially if you are lowered.